This disclosure relates to measuring resistivity in a well at two or more angles of rotation in an eccentered resistivity tool, which may be used to account for properties of drilling fluid.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions.
Many downhole tools have been developed to determine properties of geological formations surrounding wells. One such downhole tool is referred to as a resistivity tool. Resistivity tools may inject a current into the surrounding geological formation using an injection electrode. The current may return to the tool from the geological formation via a return electrode. In general, the injection electrode may represent a current-measuring electrode through which this current may be measured. By measuring the current, resistivity tools may determine the impedance, or resistivity, of the surrounding formation. Since different types of geological formations may have different resistivities (impedances), determining the resistivity of the surrounding formation may provide an indication of the properties of the geological formation surrounding the well.
A resistivity tool may be used while the well is being drilled as a logging-while-drilling (LWD) tool, or afterward as a tool conveyed by wireline, coiled tubing, slickline, or other conveyance. When used as an LWD tool, the resistivity tool is a component of a drill string. While a well is being drilled, a long string of drill pipe, generally referred to as the drill string, may be used to drill into the geological formation. In the drilling process, drilling fluid, also referred to as “mud,” is pumped down into the drill string to mechanically power the rotation of the drill bit and to help remove rock cutting out of the wellbore. Thus, in a logging-while-drilling (LWD) setting, the wellbore may be full of drilling fluid while a resistivity measurement is being obtained. The presence of the drilling fluid may disrupt the resistivity measurement of the geological formation that surrounds the wellbore. This is especially true when the drilling fluid is an oil-based mud. Previous efforts to account for drilling fluid in resistivity measurements have involved the use of multiple injection electrodes or multiple return electrodes at varying locations within the resistivity tool, which may increase the cost and complexity of the resistivity tool.